Pipe routing transforms a sub-basin runoff hydrograph from the
point of discharge in the pipe to a downstream location. As the
hydrograph flows to the downstream area it undergoes changes in
shape and distribution due to translation and reach storage
effects. This program implements the Storage-Indication
methodology, which accounts for storage effects and is derived from
the continuity equation:
ΔS/Δt = I - O
Where: ΔS = Change in storage (cubic ft
or cubic meter)
Δt = Routing time step (hours)
I = Inflow discharge (cfs of cms)
O = Outflow discharge (cfs of cms)
Please refer to the National Engineering Handbook Section 4 for
the detail of the Storage-Indication method.
Select Pipe Routing from Watershed > Hydrograph Routing menu.
This command opens a dialog for hydrograph routing. First, select
the inflow hydrograph file. Second, either design a pipe or enter
the stage-storage and stage-discharge data of a known pipe. When
design a pipe, enter pipe parameters in the pipe design dialog, the
headwater and tailwater elevations are also need to be specified
for stage-discharge calculation. If the pipe is known, select its
stage-storage and stage-discharge files, and then specify the pipe
length and its section area for calculating flow travel
time.
The numerical accuracy and stability of pipe routing is
sensitive to the routing interval Δt. The average reach travel time
is computed by dividing the flow velocity corresponding to the
average discharge for the inflow hydrograph into the pipe. If the
travel time is less than the time interval, then negative outflow
could occur and the calculation is not accurate and the program
generates a warning message asking for a smaller routing
interval.
After entering all information, click Routed Hydrograph button to generate the routing hydrograph. A dialog is opened with the tabular and graphic hydrograph data, from there you can draw the hydrograph on screen and save it to a file.
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Routing Hydrograph - Pipe Routing |
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| Pipe Routing - Pipe Design
Dialog |
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| Routed Hydrograph Dialog |